1. Field of the Invention
The present invention relates to a fastening element such as, e.g., a roof bolt, used primarily in mine and/or tunnel constructions and including a tubular member having, at one of its end facing in a setting direction, a drilling head and at its opposite end facing in a direction opposite to the setting direction, load application means, and having, in a region of the drilling head, at least one outlet opening connecting the longitudinal bore of the tubular member with an outer surface of the body.
2. Description of the Prior Art
Fastening elements of the type described above are generally known. They function primarily for stabilizing walls of hollow spaces such tunnels, galleries and the like. They are used primarily for securing to each other following each other, in a direction transverse to the wall, the wall-forming strata. In many cases, the mechanical characteristics of the layers, which lie in immediate vicinity of the wall surface, in particular, their supporting resistance, changes as a result of formation of a hollow space. Therefore, these layers need be secured to further located, undamaged or unaffected layers or strata.
A fastening element or a roof bolt of the above-described type is disclosed, e.g., in U.S. Pat. No. 4,055,051. The U.S. Patent discloses a roof bolt that is formed of a tubular element provided, at one of its end, with a drilling head and, at its other opposite end, with load application means. The interior of the disclosed roof bolt is partially filled with mortar mass. An exit channel extends through the drilling head. The setting process of the disclosed roof bolt is effected in two steps. In the first step, the roof bolt forms, with the use of an available drilling tool, a bore in the constructional component, in particular, in the ground. The drilled-of and comminuted stone, which is produced upon drilling with the drilling head of the roof bolt, is removed through outlet openings provided in the drilling head and the space between the bore wall and the outer surface of the fastening element. In a second step, a piston, which is provided at an end of the roof bolt facing in the direction opposite to the setting direction, is advanced in the setting direction, pressing out the mortar mass, which fills the interior of the roof bolt, through the openings provided in the drilling head.
One of the drawbacks of the roof bolt disclosed in U.S. Pat. No. 4,055,051 consists in that the setting process has two steps and, therefore, requires use of a special setting tool. The two-step setting process also substantially increases the setting cycle duration.
Moreover, during the drilling step, the amount of the removed and committed material, stone and the like, corresponds to the entire cross-section of the insertable tubular anchor, which adversely affects the output and increases the operational time of the drilling step.
An object of the present invention is to provide a tubular anchor that can be set in a single step with the use of a conventional drilling tool.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing in the tubular member substantially cylindrical hollow means filled with a mortar mass, with the cylindrical hollow means having, at its end facing in the direction opposite to the setting direction, an opening enabling flow of the mortar mass therethrough and having an inner diameter corresponding at least to an inner diameter of the drilling head which is formed as a crown bit, and by providing at least one longitudinal channel communicating the flow-enabling opening with the outlet opening provided in the region of the drilling head.
By forming the drilling head as a crown bit, the inner diameter of which at most corresponds to the inner diameter of the mortar mass receiving means, which is formed as a hollow cylinder, the drill core, which is formed during the drilling process can be received in the mortar mass receiving means. The drill core, when extending into the interior of the mortar mass receiving means, applies a pressure to mortar mass. This pressure is used for opening the mortar mass flow-enabling opening formed in the mortar mass receiving means. When the pressure applied to the mortar mass becomes sufficiently high, the flow-enabling opening opens, and the mortar mass can flow into the channel leading to the outlet opening in the region of the drilling head. Due to the rotational movement of the tubular anchor and, in particular of the drilling head, the mortar mass intermixes with the drillings in the region of the outlet opening and is squeezed into a space between the wall of the bore formed in the construction component and the outer circumferential surface of the tubular anchor. Further, separate mortar mass-receiving means permits to store the tubular members separately from the mortar mass which has limited storing properties.
Because the mortar mass is squeezed out by the drill core, the tubular anchor according to the present invention can be set with a conventional drilling tool and does not require the use of any auxiliary means or operational steps in order to be completely set.
Advantageously, the cylindrical hollow means includes two pistons for closing its opposite ends respectively, and a receiving space provided adjacent to the piston, which closes an end of the cylindrical hollow means facing in the direction opposite to the setting direction, for receiving this piston. The mortar mass flow-enabling opening is formed in a wall portion of the cylindrical hollow means defining the piston-receiving space and is spaced from a free end of the piston-receiving space by a distance which corresponds at least to a length of the piston measured in a longitudinal direction of the tubular member. The mortar mass, which is located between the two displaceable pistons, is displaced by the drill core in the direction opposite to the setting direction. With the displaceable mortar mass, the piston, which is located at the end of the mortar mass-receiving means remote from the drilling head, is also displaced into the piston-receiving space, which is formed in the mortar mass-receiving means, until it completely frees the flow-enabling opening. The use of this sealing piston insures that, with a sufficiently high pressure acting on the piston, the flow-enabling opening can be open under any conditions. It is to be also noted that this embodiment of the tubular anchor can be economically produced as a need in the use and, thereby, in manufacture and assembly of a complicated mechanism for freeing the opening is eliminated.
Advantageously, the outer diameter of the drilling head is larger than the largest diameter of the tubular member. This insures free-cutting of an annular slot in which the mortar mass, which is intermixed with drillings, is received.
Preferably, the outer diameter of the mortar mass-receiving means is smaller than the inner diameter of the tubular member, which insures an easy insertion of the receiving means in the tubular member.
Advantageously, the channel leading to the outlet opening, which is located in the region of the drilling head, is formed by a slot extending between the inner wall of the tubular member and the outer surface of the mortar mass-receiving means. During the manufacturer of the tubular member by, e.g., rolling a metal sheet, the slot can be formed in the inner wall of the tubular member by a separate operational step. The process of forming the tubular member is very cost-effective.
Advantageously, the channel is formed as a helically extending slot so that conventional rolling process for producing the tubular member can be used.
Advantageously, at least one hose-like bag is provided in the mortar mass-receiving means for storing the mortar mass therein to facilitate handling of the mortar mass and of the inventive tubular anchor.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction its mode of operation, together with additional advantages and objects thereof, with be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.